MDEV-23778 Derived table handler looses data on conversion from HEAP to Aria

This bug happened when the HEAP temporary table used for the derived table
created for a derived handler of a remote engine of the federated type
became full and was converted to an Area table. For this conversion
the tmp_table_param parameter must be always taken from the select_unit
object created for the result of the derived table.

mysql-test/suite/federated/federatedx_create_handlers.result

@@ -376,6 +376,50 @@ DROP TABLE federated.t1, federated.t2, federated.t3, federated.t4;
 connection slave;
 DROP TABLE federated.t1, federated.t2;
 connection default;
+#
+# MDEV-23778: Derived handler used for big derived tables
+#
+connection slave;
+CREATE TABLE federated.t1 (
+a varchar(100) NOT NULL default '123'
+)
+DEFAULT CHARSET=latin1;
+CREATE TABLE federated.t2 LIKE federated.t1;
+BEGIN NOT ATOMIC
+DECLARE i INT DEFAULT 0;
+START TRANSACTION;
+WHILE i < 70000 DO
+INSERT INTO federated.t1 VALUES (i);
+SET i = i + 1;
+END WHILE;
+COMMIT;
+END
+$$
+connection master;
+CREATE TABLE federated.t1 (
+a varchar(100) NOT NULL default '123'
+)
+ENGINE="FEDERATED" DEFAULT CHARSET=latin1
+CONNECTION='mysql://root@127.0.0.1:SLAVE_PORT/federated/t1';
+CREATE TABLE federated.t2 (
+a varchar(100) NOT NULL default '123'
+)
+ENGINE="FEDERATED" DEFAULT CHARSET=latin1
+CONNECTION='mysql://root@127.0.0.1:SLAVE_PORT/federated/t2';
+SELECT COUNT(DISTINCT a) FROM federated.t1;
+COUNT(DISTINCT a)
+70000
+INSERT INTO federated.t2
+SELECT * FROM (SELECT * FROM federated.t1 LIMIT 100) dt;
+SELECT COUNT(DISTINCT a) FROM federated.t2;
+COUNT(DISTINCT a)
+100
+TRUNCATE TABLE federated.t2;
+INSERT INTO federated.t2
+SELECT * FROM (SELECT * FROM federated.t1 LIMIT 70000) dt;
+SELECT COUNT(DISTINCT a) FROM federated.t2;
+COUNT(DISTINCT a)
+70000
 set global federated_pushdown=0;
 connection master;
 DROP TABLE IF EXISTS federated.t1;

mysql-test/suite/federated/federatedx_create_handlers.test

@@ -208,6 +208,63 @@ DROP TABLE federated.t1, federated.t2;
 
 connection default;
 
+--echo #
+--echo # MDEV-23778: Derived handler used for big derived tables
+--echo #
+
+connection slave;
+
+CREATE TABLE federated.t1 (
+  a varchar(100) NOT NULL default '123'
+)
+DEFAULT CHARSET=latin1;
+
+CREATE TABLE federated.t2 LIKE federated.t1;
+
+DELIMITER $$;
+BEGIN NOT ATOMIC
+  DECLARE i INT DEFAULT 0;
+  START TRANSACTION;
+  WHILE i < 70000 DO
+    INSERT INTO federated.t1 VALUES (i);
+    SET i = i + 1;
+  END WHILE;
+  COMMIT;
+END
+$$
+
+DELIMITER ;$$
+
+connection master;
+
+--replace_result $SLAVE_MYPORT SLAVE_PORT
+eval
+CREATE TABLE federated.t1 (
+  a varchar(100) NOT NULL default '123'
+)
+ENGINE="FEDERATED" DEFAULT CHARSET=latin1
+CONNECTION='mysql://root@127.0.0.1:$SLAVE_MYPORT/federated/t1';
+
+
+--replace_result $SLAVE_MYPORT SLAVE_PORT
+eval
+CREATE TABLE federated.t2 (
+  a varchar(100) NOT NULL default '123'
+)
+ENGINE="FEDERATED" DEFAULT CHARSET=latin1
+CONNECTION='mysql://root@127.0.0.1:$SLAVE_MYPORT/federated/t2';
+
+SELECT COUNT(DISTINCT a) FROM federated.t1;
+
+INSERT INTO federated.t2
+  SELECT * FROM (SELECT * FROM federated.t1 LIMIT 100) dt;
+SELECT COUNT(DISTINCT a) FROM federated.t2;
+
+TRUNCATE TABLE federated.t2;
+INSERT INTO federated.t2
+  SELECT * FROM (SELECT * FROM federated.t1 LIMIT 70000) dt;
+SELECT COUNT(DISTINCT a) FROM federated.t2;
+
 set global federated_pushdown=0;
 
 source include/federated_cleanup.inc;

sql/derived_handler.cc

@@ -120,8 +120,6 @@ void derived_handler::set_derived(TABLE_LIST *tbl)
   table= tbl->table;
   unit= tbl->derived;
   select= unit->first_select();
-  tmp_table_param= select->next_select() ?
-                   ((select_unit *)(unit->result))->get_tmp_table_param() :
-                   &select->join->tmp_table_param;
+  tmp_table_param= ((select_unit *)(unit->result))->get_tmp_table_param();
 }